bonafide11
Worker
They already have two UAs. +1 sight on all land units and half-price tile buying. I still don't see a great deal to recommend America, they're a grab bag of, "That's nice, I guess" abilities that come up for limited periods of time in specific situations. They get good scouts, but that period of the game passes quickly, and the Shoshone can make a playstyle out of that far better than they do.
+1 sight is nice enough in military applications (especially one artillery show up), but you can usually have another unit move up one hex, spot whatever you want to shell, shell it, then move the scouting unit back again. So +1 sight is nice, but not anything that holds a candle to Shaka's cheap promotions, or Germany's cheap army, or a real warmongering unit.
They get a fast musketman who generates golden age points. Not only is the musketman a not-particularly-good unit type in the first place, the "ignores terrain" aspect of him isn't always useful, and golden age points are not that valuable. Compare this to the Pracinha, whose golden age points are much more valuable since they get extra Tourism and Great People out of them. The Minuteman is just a lacklustre unit with a bunch of non-focused bonuses tacked on.
Then you get the B17. It's a bomber that's less likely to get shot down. Firstly, I can't remember a time when I was using bombers that I didn't have air-superiority. Sure, I wouldn't turn down extra evasion, but it's not a huge bonus. Secondly, the game's almost always decided by this point. The fact that you've got bombers at all tends to indicate that you're going to win, not the fact that they're B17s.
America has lots of small bonuses that don't focus them in any particular direction. They have two unique units, which would indicate that they're a warmonger, but they don't really get much in the way of bonuses to help them wage war. They can buy tiles at half-price, but you hardly do that in your average game. They get extra sight, which is good for short bursts of the game and merely convenient for the rest. They get extra golden age points and a slightly upgraded musket dude. They get a good bomber.
None of it has any focus. Sure, you can do well as America, but really you'll be doing well in spite of your civ choice rather than because of it.
I couldn't have said it better. America is just a hodgepodge of random mediocre bonuses that really don't help you in any one particular way. They're probably the worst designed and least imaginative civ in the game. Just a very boring civ to play as.